1. Field of the Invention
This invention relates to a method and apparatus for automatically preparing one or more stacks of sheets, each stack having at least two substantially straight edges that meet to define a corner and, specifically, where preparing constitutes corner rounding, notching, hole punching or edge marking the stack.
2. Description of Related Art
When making sheets, such as of X-ray film, it is necessary to cut the corners round which is referred to as corner rounding. This is necessary so that the film can be readily handled in commercially available X-ray exposure equipment.
Manually aligning the corners of a film stack and die cutting the stack corners is known. See U.S. Pat. Nos. 3,125,920 and 3,516,317. However, this process is slow and alignment is unreliable.
Automated edge trimming is taught in U.S. Pat. No. 968,014 where a stack of sheets is vertically oriented in a "V" trough for aligning and cutting two edges, but not the corners. Automated on-line corner rounding by notching a running web and cutting at the notch, or by slitting and chopping the web into sheets and corner rounding individual sheets, is disclosed in U.S. Pat. No. 4,407,177. However, these automated methods of on-line corner rounding present problems with reliable alignment and rapid changeover to different sheet sizes.
It is an object of this invention to provide a method and apparatus for on-line or off-line preparation (such as corner rounding, notching, hole punching or edge marking) of sheets which is simple, accurate, operates at high speeds and requires no time for changeover to different sheet sizes.